Impact of operating conditions on the flux changing rate during dead-end microfiltration process

Dead-end microfiltration experiments with the activated sludge suspension from submerged membrane bioreactors were performed to determine the critical flux, which is a very significant factor to indicate the membrane fouling in microfiltration process. In this study, the critical permeation fluxes were measured by successive variations of transmembrane pressure (step by step technique) under different operating conditions (temperatures, stirring rate and concentrations of the mixed liquor suspended solid [MLSS]) using polyvinylidene fluoride membranes with a pore size of 0.1 mu m. A study of the impact of various operating conditions on the fouling rate when the critical flux is achieved was especially made. The experiments revealed that: the increase in stirring rate leads to a decrease in the rate of fouling; the fouling rate decreased with the increase in temperature when it was less than a certain values, after that, it increased with the continuous increase in temperature, while the variation of the concentration of the MLSS has a negative influence on the membrane fouling. The results obtained from the experiments can provide reliable information to the optimization of operating conditions to alleviate membrane fouling.